Re: missing stem

[Simon Albrecht]

Hello Bogi,

On 23.11.2015 00:50, Bogi Lützen wrote:
> Please help me with this little problem.
>
> This is just one of my efforts, but in all of them I miss the stem on the
> first g'2:
>
> \version "2.18.0"
>
> {
>                 
>                 <<{c''1^~|\stemUp c''2 c''4 c''| c''1}{\stemDown g'2 a' |g' a'4 a'| 
> g'1}>>
>                 
>
>         \bar "|."
> }

first: your code example can be made much easier to read if you add some 
spaces and line breaks, and get indenting right (this is done 
automatically by Frescobaldi, a great program for working with LilyPond 
files <http://frescobaldi.org>):

%%%%%%%%%%%
{
  <<
    {
      c''1^~ |
      \stemUp c''2 c''4 c'' |
      c''1
    }
    {
      \stemDown g'2 a' |
      g' a'4 a' |
      g'1
    }
  >>
  \bar "|."
}
%%%%%%%%%%%

If you run your snippet, you should get three warnings in the log, one 
of them saying that ‘maybe your input should specify polyphonic voices’. 
And that is the problem here: your code only produces only one ‘voice’ 
(in the LilyPond sense of the word) and you need two of them.
The most basic way to achieve that is inserting \\ between the music 
expressions:

%%%%%%%%%%%
{
  <<
    {
      c''1^~ |
      \stemUp c''2 c''4 c'' |
      c''1
    }
    \\
    {
      \stemDown g'2 a' |
      g' a'4 a' |
      g'1
    }
  >>
  \bar "|."
}
%%%%%%%%%%%%

This will work in this small example. In any more complex situations, 
you should create voices explicitly with \new Voice, and distinguish 
them by \voiceOne, \voiceTwo etc.

Did you read the Learning Manual 
<http://lilypond.org/doc/v2.18/Documentation/learning> already? It gives 
a great, ‘must-read’ introduction into working with LilyPond.

H(ope)T(hat)H(elps),
Simon